[node-split] Extend systest with option to add split node setup

[jellonek]

This commit can be used as a testing platform for changes provided in #6521.

Note: split node setup will always deploy non smeshing node (node-service, pod named as smesher-X wher X is the biggest number) to which there will be deployed connected n-1 smeshing/client nodes (node-client, pods named activation-X). Because of that - node-split-size has to be set to 0 (default value) or >1.

On makefile or make run level that's controlled by setting e.g. node_split_size=3.

Extracted from #6506.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 77.1%. Comparing base (49bbb0b) to head (d4a8ce9).
Report is 1 commits behind head on node-split-poc.

Files with missing lines	Patch %	Lines
api/node/server/server.go	0.0%	4 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           node-split-poc   #6522     +/-   ##
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- Coverage            77.2%   77.1%   -0.1%     
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  Files                 342     342             
  Lines               45839   45844      +5     
================================================
  Hits                35391   35391             
- Misses               8330    8342     +12     
+ Partials             2118    2111      -7     

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